Diesel engines typically have higher thermal efficiency and lower fuel consumption rates than gasoline engines due to the increased compression ratio of the diesel combustion process and the higher energy density of diesel fuel. Consequently, diesel engines have a higher thermal burn efficiency which leads to improved fuel economy as compared to gasoline engines with similar output.
Internal combustion engines combust an air and fuel mixture within cylinders of the engine to produce drive torque. Engines can include a turbocharger that increases torque output by delivering additional air into the cylinders. One traditional turbocharger includes a variable nozzle turbo (VNT). VNT's include vanes that can be adjusted to regulate the amount of air delivered through the VNT. The vane position ranges from a fully-open position to a fully-closed position. In the fully-open position, the VNT delivers a minimum amount of air to the engine. In the fully-closed position, the VNT delivers a maximum amount of air to the engine. The vanes can be positioned between the fully-open and fully-closed positions to provide an intermediate amount of air to the engine. A vane solenoid adjusts the vane position based on a vane control signal and a vane control sensor generates a vane position signal indicating the actual vane position.
Diesel engines often include a turbocharger for increased air flow to meet emission requirements and performance standards. Boost (increased air flow) is typically calibrated based on sensed parameters. Typical indicators for engine running conditions are intake manifold temperature, coolant temperature, engine rpm, fuel quantity and injection timing. In diesel engines with waste-gate turbochargers, the boost map is typically set up for normal (warm) engine running conditions with sufficient engine load, normally experienced when the vehicle is moving. Typically, the turbocharger is not capable of producing boost when the vehicle is stationary with minimal engine load. In instances where normal conditions do not apply such as cold/hot ambient conditions, certain engine controls such as injection timing would be adjusted with minimal impact.
While diesel engines offer many advantages, one common drawback is their inability to warm up quickly in cold ambient temperatures. As a result, a vehicle heater sometimes requires a long time to produce heat for the vehicle cabin. Typical methods to accelerate engine warm up times in cold ambient temperatures include incorporating a butterfly valve exhaust after treatment device (exhaust restrictor) or external fuel operated heating device. The exhaust restrictor provides backpressure on the engine, increasing engine load and allowing for increased fuel consumption. Typically, the exhaust restrictor is external and additional to the base engine. In another example a fuel operated heater (FOH) is used. An FOH acts to increase in vehicle heating performance by acting as a space heater. FOHs are usually independent of base engine hardware and controls.